Hypothesis
by A Beauty to the Rhythm
Summary: After Castle and Beckett survive their encounter with the tiger, Castle comes up with a series of highly scientific experiments to find out exactly how Kate feels about him. Then he hatches a plan that just might get her to finally embrace those feelings. A Season 4 story that takes place after 'Cuffed.' Entry for the 2014 Winter Ficathon.
1. Concocting

_A/N: Happy Winter Hiatus! I've been off the grid for a little while, but I do hope you enjoy what I'm cooking up for you in this story. All thoughts and constructive criticism welcome along the way, as I only have a smattering of an idea of where this is going to end up. Endless thanks to Meg for her unwavering friendship._

_Lately, I've been craving a bit of a throwback to old school Caskett, so this is a Season 4 fic that picks up a few days after 'Cuffed.'_

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><p><strong>Chapter One<br>**Concocting

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><p><strong>hypothesis<strong> |hīˈpäTHəsis| noun (pl. hypotheses |-ˌsēz| )  
>a supposition or proposed explanation made on the basis of limited evidence as a starting point for further investigation.<p>

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><p>He's been so patient.<p>

That day on the swings, he'd understood her perfectly even though she'd avoided the actual words - _wait for me_ - with the fluidity and grace of an ice skater.

But after spending hours with her locked in that basement, he's not sure patience is what she needs from him anymore. Had she really been throwing him clues? Or is she still stubbornly fighting their chemistry like she's always done?

Castle rubs his hands together. The right one is still somehow warmer after she'd allowed him drag it down the curve of her side. Well, maybe _allowed_ isn't the right word. He'd seen the angry pinprick where she'd been tranquilized, and he couldn't have stopped himself if he'd tried. He just had to touch. Any initial concern for her health had been swiftly chased away by something thick and breathless when he'd felt her bare skin under his fingers.

And then, to his absolute awe, she jumped under his touch, trembled really, and maybe it's his deluded fantasies bleeding into real life, but he swears it wasn't a twitch of surprise or cold, but one of delight. Pleasure.

And when they were pushing against that frickin' massive metal container … she'd told him he better not be enjoying himself. He'd answered with an _I'll let you know in a minute_, but his body was reacting already. The effort it was taking to control himself took all the teasing out of his voice, making him sound considerably less cheeky than he normally would when laying innuendo on her.

Because he definitely had let her know. He'd felt the exact moment she stilled, the moment she realized how hard he was against the back of her thigh. Had she really pressed back into him? The pressure was infinitesimal, but he doesn't think he imagined it.

And then that comment. God, that comment.

_Next time, let's do it without the tiger._

If it had only been one of those things, he might have been able to keep going on as they had been. But all three of them?

Screw patience.

Richard Castle has a plan.


	2. Craving

_A/N: Holy cow, I'm stunned by how many of you are interested in this story! :) This chapter is dedicated to my awesome friend LaLa111202. It is a blast talking about writing with you. To watch a video of the ridiculous game they play in this chapter, Google 'plunger game.' I do realize this chapter is getting out of character, but it's fun to play with Rick's crazier side!_

_And now: on with Castle's Plan._

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><p><strong>Chapter Two<strong>  
>Craving<p>

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><p>Firstly, he needs to know if she does actually want him.<p>

In bed.

Sure, there's been mountains of innuendo, heaps of shameless flirting, and that thing she said once about the hot wild thing she likes to do that he suspects has nothing to do with putting killers behind bars … but he has to be sure.

The next time they're at the precinct together, he hands her a coffee and takes a deep breath. But then she smiles. It's pathetic, that all she has to do is smile and his bravado goes out the window. He'd been prepared to come on strong and bust her door down (figuratively, of course) and she'd melted him with one little curve of her lips.

The evidence from the basement seems insubstantial now, faded into myth over the three days since they were cuffed together.

More evidence. That's what he needs. Stronger evidence to bolster his case.

All morning he thinks, staring at her even more than usual. Which is impossible, because lately he's been staring at her all the time.

He wriggles in his chair. He's never loved such an uncomfortable piece of furniture in his life. He'd surreptitiously brought in a bottle of Febreze and given it a good spray a few weeks after he started shadowing her. A dozen times he's suggested purchasing a new chair: top of the line, ergonomic, hydraulic, the works. They both know he'd never do it. Four years and they're both a little bit attached to that rust-colored piece of crap.

Mentally, he whips himself back on task. Before he lets himself take a Richard Castle-sized wrecking ball to that fabled wall of hers, he wants to know exactly what it is that she wants (hopefully him). Then, and only then, he'll try to hold a mirror up for her and make her see it, convince her to stop hiding from it. He just has no idea how to get the information he needs.

He makes his first breakthrough while he's brewing their third pair of coffees for the day, while the silver frothing wand splutters deep in the beaker of milk. Next to the battered and abandoned Mr. Coffee from the precinct's pre-Castle days, there's a new notice on the bulletin board. The precinct is holding its annual Sports Day in two weeks. His mind starts percolating with a million ideas of how to work some justifiable Beckett-touching in. There are some activities he'd be embarrassingly shitty at, like basketball and wrestling. But a three-legged race? Definite potential.

Hold on a second. Something tugs at him. A memory of laughing with his mother over a video he'd found on YouTube.

He's got the perfect game. One that will draw her out and give him a definite answer about one of the three things he needs to know before he can start his seduction.

He's going to be the butt of a lot of jokes at the 12th for a long time (like he isn't already).

It will be totally worth it.

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><p>After Beckett and Castle win the three-legged race, they collapse onto a bench in Central Park. She leans down to untie the three red scarves that bind her left leg to his right. It's breezy for May, but he'd worn basketball shorts anyway, hoping for a little skin to skin contact. Unfortunately, she'd shown up in black yoga pants. He can't really complain though. It's been totally <em>awesome<em>.

Her long fingers work at the knot at their ankles. It's taking a while; she can't quite get a grip on the fabric with her short nails, but Castle is 100% okay with that. Quite a lot of her back is exposed by the cut of her black lycra tank top and the braid tucked over her right shoulder, and he has to grit his teeth to stop himself from leaning forward and licking the sheen off of her vertebrae. She's still flushed with the glow of their recent victory, and he suddenly realizes that when they finally do this relationship thing, he might actually start working out just so he can accompany her to the gym.

She's laughing and saying something about the looks on someone's faces when Castle looks across the field and snags Esposito's attention, flicking his eyes to the black duffel bag next to the soccer goal. Espo nods and starts unpacking the bag.

For a second Castle loses himself in the sensation of Beckett's fingers brushing over his thigh as she removes the last scarf. God, he's so gone for her.

She shakes her leg out and stands up.

"I think the next game's starting," she says, noticing the group of cops lining up into four rows on the edge of the field. "What's this one, potato sack relay? What do you say we go kick some more ass, Castle?"

"Bring it on," he replies, and trots after her. They join the group just as Esposito and Ryan start explaining the rules of the game to the other cops. This particular favor had cost him bigtime: two weeks without the Ferrari, and insider information in case Espo wanted to start a pool about how Beckett would react to this. He'd recommended betting on the use of a phrase that involved the word shit, and that she'd leave the park before participating in the kickboxing tournament, even though it was her specialty.

Castle didn't dare put any money in the pool. If she found out about it … let's just say he really doesn't want to join the Vienna Boy's Choir.

Ryan claps loudly to get the crowd's attention. "Okay, everyone, this is called the Plunger Relay." Castle watches warily as Beckett's brows knit together in confusion.

"One person from each team stands at the end of the field with a roll of toilet paper between his legs," Ryan continues. The cops start to grumble. Maybe this wasn't such an awesome idea. Ryan demonstrates by placing a roll of toilet paper between his thighs, hole pointing out. Someone whistles, and Esposito picks up the explanation.

"The next person has to run across the field with a toilet plunger between his legs. When he reaches the end, he has to put the plunger through the toilet paper roll." He ignores the lewd comments and catcalls and keeps talking. "Once they've succeeded, the plunger becomes the new roll holder, the ex-roll holder runs the plunger to the next team member, and so on and so on until all members have plunged."

"We are totally going to own this game!" Castle brags. Loudly.

A few cops look backwards. He thinks they might be the ones with money riding on the next words to come from Beckett's mouth. Sure enough -

"Castle," she hisses. "You have got to be shitting me."

Esposito hides a grin.

"This is ridiculous," Beckett carries on. "Old drunk ladies play this game, Castle." He can see her cogs turning. She rounds on him suddenly, eyes clear and blazing. "This was your idea, wasn't it?" Her index finger drills into his sternum and it hurts.

He looks down at her and cocks an eyebrow. He loves her in heels, but he's glad she's in running shoes today. He takes a step into her, leering over her.

She doesn't cower; she never has. Her spine straightens like a rod.

"If you don't want to play, Beckett, we can sit this one out."

"As if. Are you sure you're _up_ for it though?"

Dammit, how does she still have the upper hand? Her voice is lilting and teasing, like the idea of him putting something between her legs doesn't bother her at all.

Oh, wait, there it is. She swallows a little more forcefully than usual. Castle takes advantage of the chink in her armor.

He sets his voice to stun mode.

"Oh, trust me, Detective. I'm up for it. My aim is exceptional."

Something flickers in her eyes, but it's gone before he can grab it and seal it away in an evidence bag. Beckett crosses her arms and takes up position at the back of the nearest line. She might as well have just said "harrumph." Castle stands behind her, close enough for her to feel his body heat.

Even though she's unimpressed by the game, she doesn't seem to have caught on to his plan.

Esposito blows his whistle and the first four players take off down the field, plungers waggling obscenely out in front of them. Castle wishes Beckett's back wasn't to him so he could read her, wishes everyone wasn't cheering so loudly so he could zone in on the evenness of her breathing. He didn't really want to give her this much time to prepare; he knows what Beckett can do with a minute and he really needs an unguarded reaction.

Suddenly, it's her turn to plunge. Esposito and Ryan are in stitches watching their boss stumble gracelessly towards Karpowski, plunger waggling between her thighs.

"Be gentle with me, Beckett," Karpowski pleads, and Castle can feel Beckett's smile from a twenty yards away. Her body loosens as she laughs, finally pulled back into the spirit of the day and the ridiculousness of the moment. He can't take his eyes off her when she smiles like that. Then she tucks the roll of toilet paper between her legs and he's never been jealous of an inanimate object before but hey, there's a first time for everything.

When Karpowski hands him the plunger, he thanks her a little too sincerely and she looks at him like he's crazy. She'll never know how much she helped his cause by bringing Beckett's guard down.

He feels like an idiot as he makes his way towards her, and doesn't even notice that their team is in the lead. She's studiously avoiding looking at him, but he won't take his eyes off her. Not now.

He's a yard away when she finally focuses on him. Their eyes lock, releasing that same stomach-flipping rush of adrenaline they get whenever they have theory sex, or whenever they get a little bit to close to talking truthfully about their relationship.

He flicks his eyes down to set his aim, then goes the rest of the way blind. The world collapses in on them, time slowing as he prepares to capture her reaction.

He knows her tells. A rosy, mottled blush spreads from the center of her chest, creeping out from underneath the cover of her tank top, spreading over her collarbone and up her throat. Her pupils contract at first, then expand until there's hardly any hazel left.

Her lips fall apart.

She stops breathing.

The tip of his plunger slides through her toilet paper roll on the first attempt. If his hands touch her hips, it will disqualify them, so he balls his hands into fists and digs his nails into his palms to keep from grabbing her and pulling her even closer. At the end of the slide, their hips meet. His knees are bent, so his momentum knocks her just slightly upwards and back.

If her reaction is even one millionth of what it would be like if they were doing this for real, he's never going to survive actually having sex her.

They're both paralyzed by the moment, until the shouts of the rest of their team bring them back. They're about to lose their lead.

Castle pulls out. Emboldened by her reaction and high as a kite on love, he takes a risk. He winks at her. Her responding flash of anger scatters some of that mesmerizing desire rippling in the depths of her eyes, but she doesn't have time to berate him. She grabs the wooden handle of his plunger viciously, wrenching it from between his legs before bolting off for the finish line.

He smiles, but not because his team won.

The evidence is absolutely unassailable.

Kate Beckett totally, definitely, 100% wants to have sex with him.

She doesn't say goodbye to him before he sees her ducking into her Crown Vic and pulling away from the curb. The sun is low in the sky, but there's plenty of day left. He settles in to watch the kickboxing tournament on the lawn, the rustle of cash changing hands behind his back as Esposito collects his winnings.


	3. Caring

_A/N: _Apologies in advance if this story seems more out of character than my usual stuff. I've just finished a Season 2 marathon with my SFAM (Sister from Another Mister) in an effort to get her hooked on the show, and I think it's affecting my writing - Castle keeps acting like his cheeky S2 self even though he's supposed to be S4 subdued and chivalrous. Still, I hope you're having fun imagining this craziness with me.__

_This chapter is for EvaKAlways - I'm so glad we met through this show :)_

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><p><strong>Chapter Three<strong>  
>Caring<p>

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><p>He waits a week before administering his next test, mostly because it takes that long for Kate to warm up to him again. He's not sure why she was ashamed of letting a little emotion show, but that's something he'll ask her during 'The Confrontation.' Assuming she passes all of his tests.<p>

Castle pops a sticky pork dumpling into his mouth and looks across his dining room table.

"So. You're all clear on the plan?" he asks.

"Dad! How many times do I have to tell you? Quit talking with your mouth full," Alexis says, her spring-loaded chopsticks scraping at the bottom of her box of Singapore noodles.

"Richard," his mother says, "Do you really think this is the best idea?"

"Well, it's the best I've got. It's the only thing I can do to make her think I'm in serious danger without me having to outright lie to her."

Martha takes a drag of her martini. "So you're asking _us_ lie to her instead."

"Acting, Mother. I'm asking you to act."

Martha brightens. "Well then, consider it acted."

Alexis just nods, a smile playing on her lips. Anything to goad Beckett and her father into action. Because, honestly, everyone who knows them is really tired of waiting.

Castle fishes his phone out of his back pocket and holds the power button down.

"Right then. Let's get started."

He slides his thumb over the screen and the phone goes dark. It's only then that he wonders if what he's doing might be very, very wrong. He pushes down the feeling and pastes a smile on his face.

"There. Now we just wait."

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><p><em>Where the hell is he?<em>

Beckett stares at the murder board. They've been to the crime scene. They've canvassed the neighbors. They've questioned and ruled out one potential suspect. Traffic cam footage came in hours ago, and they've combed through at least half of the vic's finances.

She stares at the murder board, but she's not thinking about the case. Hasn't been for the past half hour, at least. Because he still hasn't called back.

She flicks her wrist to check the time. Again. Five hours, eighteen minutes, and something like forty-two seconds since she called this afternoon to give him the crime scene address. More than twenty-five hours since the last time she actually talked to him, watching him waving goodbye with a cheery smile as the elevator doors closed on him, the NYPD logo sliding to replace his face.

Esposito slides his chair over. "Yo. Any word from Castle?"

"Nope."

"Huh. Maybe he had a meeting for his book."

"Yeah, maybe."

He always tells her, though. These days. Usually texts her throughout his meetings with silly little jokes, things that make her paperwork days go a bit faster. She can't identify the weird feeling in her chest. Her fingers fly up to her scar, out of habit, pressing and circling.

"You okay?" Esposito asks.

She nods. Knows that she isn't going to look convincing even if she tries. Esposito, in a rare moment of grace, slides his chair back to his desk and doesn't press the issue.

Something is not right. There was a time when she wished Castle would just stop pestering her, but those days are long gone. He's not gone radio silent on her in … well, since the sniper, and that was really her fault, wasn't it?

She won't text again. She's sounded desperate enough already in the three that she's sent. Sheesh, three texts.

_You're going soft, Beckett._

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><p>She calls it a night two hours later, just in time for the boys to catch last orders at the Irish pub one block over. It's only nine-thirty, but it is a Sunday.<p>

In the cab on the way to her apartment she tries to call Castle again, biting her lip to keep from leaving a message. He's a grown man, completely capable of taking care of - wait a second. He's Castle. He appears to be a grown man, but he definitely isn't always capable of taking care of himself. _Except for when he takes better care of you than _you_ can, _a little voice whispers in her ear.

"Turn around." The words are out before she realizes they're hers. "Please. Turn around please." She gives the driver Castle's address and settles in for the drive. She has to sit on her hands to keep them from shaking.

"Castle, open the door!"

She's only knocked once, but she's already adding verbals. Easily explained. Protocol. Not nerves. Habit. Right.

The door flies open to reveal Martha in fluttering black and white palazzo pants, a dozen gold necklaces covering her neck and half of her electric blue blouse.

"Detective Beckett, darling, why all the shouting?" Her smile drops. "Is something wrong?"

"Hi Martha. No. I mean, I'm so sorry to bother you, I'm sure it's nothing. It's just that I haven't heard from Castle all day, but if he's here I'll just go, and I'd really appreciate it if you don't tell him I came- " The words are pouring out because she has to get out of here before he sees her, because she can't hide anything from that damn man and he'll read the concern on her face before she has a chance to school it away.

Beckett turns to go but stops when she feels Martha's hand on her arm.

"But Katherine, he's not here. Darling, I haven't seen him since last night. You're not working on a case are you? Is he in danger?"

"I am working a case, but it just came in this afternoon. Castle hasn't been involved."

Over Martha's shoulder, Beckett sees another flash of red cross the living room. Great, Alexis is here too.

"Detective Beckett? What are you doing here?"

Martha gently pushes Alexis towards the kitchen.

"Alexis, sweetheart, why don't you go make us all a nice tea. Chamomile, I think."

Alexis shoots them a look, but disappears to the kitchen.

Beckett groans and tries to apologize to Martha again. She's been extensively trained to keep relatives from going into panic mode and here she is, panicking enough for all three of them. This evening is just an epic fail.

"Darling. Come inside. Sit down. I'm sure there's a reasonable explanation. Let's call him."

Her coat is hanging in the closet before she even registers that Martha has taken it off.

"I've been trying all day." Beckett's voice sounds so small and helpless to her ears, but it's probably just her imagination.

Martha leads her to the couch and they both sit.

"Well, what else can we do … I'll call Paula and Gina and see if he had anything on at Black Pawn. And maybe Alexis has spoken to him since I saw him last."

Good. This is good. Martha is anchoring her. She's taking control, offering solutions in a way that is so familiar, but Beckett can't put her finger on it until - oh.

Oh.

She hasn't been on the receiving end of maternal comfort in thirteen years. No wonder she didn't recognize it at first. Beckett tries to lets her gratitude for Martha's support edge out the creeping black sorrow that surfaces whenever memories of her mom sneak up on her. This is definitely a mother situation. Her best friend is missing. She's a cop and her best friend is missing and she's being totally useless.

Oh wait - she's a cop.

Beckett pulls out her phone and speed dials the precinct.

"Hey Rob, it's Detective Beckett. Who's on the tech desk this time of night? Great. Can you put me through?"

She waits while Rob transfers her to Officer Stephens, leg bouncing up and down furiously. Martha's already on her own phone speaking to Paula.

Suddenly, Martha's palm settles on Beckett's knee, light and comforting, and the shaking stops instantly.

What is even going on here, and why does she just want to hug this woman and start sobbing into her neck? And why can't Castle just be here, filling the space with his ridiculousness and his smile and his larger-than-life personality? What she wouldn't give to know where he is, what she wouldn't do to -

Officer Stephens' voice cuts into her thoughts before they get really serious. She's thankful, because she's freaking out and it's not like her at all. She just can't handle herself right now.

"Stephens, hi, it's Beckett. I was wondering if you could do a cell trace for me?"

"Sure, ma'am, what's the number?" Stephens is only a few months out of the academy and bit starry-eyed in her presence, and even though it makes her feel ancient, he refuses to stop calling her ma'am.

She gives him Castle's number.

"You working a case this time of night on a Sunday, ma'am?" She can hear the clicks of the keyboard as he searches. "Er - is this the kind of trace I shouldn't keep a record of?"

Beckett's exasperated, she just wants to know where Castle is.

"What do you mean?" she asks.

Stephens clears his throat. "It's Mr. Castle's phone, ma'am."

"Yes, I'm aware of that."

Oh. He thinks she's making a personal request.

Crap. She is.

"He's missing," she says. Her voice is hard. She's going to play it like this isn't a misuse of police resources. It's not like she's requesting a track on a cheating spouse. She'll get away with it, because she's Beckett, and this is a one-time thing anyway. "Just do the trace."

"Right, ma'am. Let's see here … phone must be off. I'll keep tabs on it though. If anyone powers it on, I'll call right away and let you know where he is. Do you want me to pass it onto Grady when he takes the next shift?"

"Yes, please. You can make record of it, Stephens, don't worry. I'll deal with Gates later. And thank you for this."

She hangs up the phone and turns to Martha. The older woman shakes her head, eyes brimming with sympathy and a healthy dose of worry, and Beckett doesn't have to ask to know that Paula and Gina were dead ends.

Alexis arrives bearing a tray with three heavy ceramic mugs of tea. She sets them down and levels Beckett with a terrifying teenage glare.

"What's wrong, you guys? Is it my dad?"

"He's just not answering his phone, Alexis, no reason to worry yet." Even as she says it her voice falters. _Damn it, Beckett, get it together. You're the cop here! _"When did you last hear from him?"

"He tucked me in last night." As soon as it's out Alexis blushes, ashamed that she's eighteen and still gets tucked in. "I haven't heard from him today, but I just assumed he was with you."

Beckett shakes her head.

"He was here this morning though. There was a mug on the counter and the coffee maker was warm when came down," the girl adds.

The three of them sip their teas in worried silence.

"I'm sure he's fine," Beckett says again, sounding less confident by the second. "But I can't just sit here and wait for a call. If he was definitely here this morning, we can't put an APB out yet; he hasn't been gone long enough. I'm going to head over to the Old Haunt. Anywhere else I can check that he might be?"

Alexis and Martha give her a few ideas, and insist that she come back afterwards, no matter how late it is, to wait with them.

Before she shuts the door behind her, Beckett looks at the two strong, wonderful women Castle's been blessed with. Does she belong in that category? She shivers, because she realizes, for the first time, that she wants to. Belong.

_Oh, Castle. Just be okay._

* * *

><p>It's well past midnight when Beckett returns to report in. Alexis and Martha are huddled together on the couch watching the Discovery Channel, but they're obviously not paying much attention to the mysterious evidence of electricity in Ancient Egypt.<p>

He's still missing, of course. That much is obvious. Beyond that, there's not much to say.

Martha offers her a glass of wine with a watered down version of her trademark flourish, then returns to Alexis. Beckett sinks onto a barstool and downs the wine in the space of five minutes. When she thinks the other two aren't looking, she tries to press the wrinkles out of her forehead. It's just too much. She worries about him enough when they're on the job, when he's in his stupidly adorable bulletproof vest, all bright-eyed and bushy-tailed. At least in those situations she has a modicum of control. She can protect him, be his backup. Having him just disappear, with no way to find him or be there for him, that's a scenario she has never played through. She's thoroughly unprepared.

And there is probably something in this that speaks to the memories of the night her mom was killed. Waiting for her to turn up at the restaurant. Wondering where she was and just assuming she was fine, just caught up at work. Her stomach turns at the thought of Castle slumped lifeless in some filthy corner of the city, blood streaking the wall and coagulating underneath him. She presses her hands to her mouth to stop from throwing up.

Shit. Her eyes feel prickly. This is really not good.

Martha slides her phone out from between the couch cushions. She finds the text stream to Alexis' phone and types as quickly as she can while Beckett's distracted.

_Richard. I think that's quite enough. Katherine is crying in your kitchen._

Beckett's phone rings two minutes later, 'NYPD Switchboard' flashing on the Caller ID. She inhales hard with her mouth closed, trying to clear her nose so whoever's on the other end doesn't know she's on the verge of a breakdown.

"Beckett." It's almost convincing.

"Detective Beckett, it's Officer Stephens. Castle's cell has just gone live, do you have a pen and paper for the address?"

"Yes." She doesn't, but she's good at memorizing addresses, and this is one she definitely won't forget.

Stephens reads it off. "Do you want me to call in for backup?"

"No, I'll get a visual and call from the scene if there's anything suspicious." It comes out before she can think. Years of training. Like this is just another case and not the potential kidnapping or murder of her -

Of Castle.

She hangs up and fills Martha and Alexis in. There's a whirl of activity and then she's gone, calling a promise after her that she'll bring him back.

* * *

><p>It's a diner.<p>

A_ freaking_ diner.

And there is Castle, in a booth by the window, visible from a block away in the fluorescent glare of the overheads, eating waffles and drinking coffee at one in the morning like it's something he does every day.

It's shocking how quickly Beckett's heavy mire of worry turns into acerbic anger.

The bell tied to the diner door falls off as Beckett slams it open with more force than necessary. A lot more force than necessary.

The waitress nearest the entrance starts to say something but Beckett silences her with a frightening glare before stalking over to Castle's table.

There really aren't words to express how upset she is, but "Where the hell have you been?" will have to do. It comes out as a hiss.

Castle looks afraid. Really afraid.

"Here…?" he squeaks.

"Do you have any idea how worried we've - how worried your mother and daughter have been?"

She wants to stab a fork into the glint that appears in his eye at the word 'we.'

"Castle, what the hell have you been doing all day?"

He gestures at the open laptop next to him, the text of his next Nikki Heat on the screen and a legal pad full of scribbles next to his plate of half-eaten waffles.

"Writing." His voice is feeble, and he looks very sheepish.

"All day."

"Yes."

"Here."

"Yes. Well, I did pop out to pick up some dry cleaning." He nods at the pile of perfectly pressed shirts tied up in a plastic bag on the bench seat opposite him.

"You pick up your own dry cleaning?"

"What kind of question is that, Beckett?"

"Answer me."

"Yes, I pick up my own dry cleaning. Even though I'm rich, I don't see the point in wasting money when I can just go out and get some fresh air and sunshine and pick up my own damn shirts." He narrows his eyes. "Is this an interrogation?"

"Where is your phone?"

He taps it where it's laying on the table, connected to his computer via a USB cable.

"And you just felt like ignoring all our calls and texts all day?"

"It was dead. I only just started charging it - I didn't have a cable until Eve let me borrow hers." He nods towards the waitress who's still eyeballing Beckett over the damaged bell. "She just started her shift half an hour ago."

"Right." Beckett has half a mind to ask the waitresses to corroborate Castle's story, but she reminds herself that it doesn't matter. That he's here and unharmed.

"Wait a minute, did you _track _me?" Castle asks.

He would put two and two together, wouldn't he? Realize that the only way she could have found him here was if she tracked him.

"Don't make me smack that smirk off your face. Pack up your stuff, Castle. I'm taking you home."

"Just don't hurt me," he pleads, but as soon as she turns her back his pout morphs into a massive grin.

And as if Beckett didn't have enough reason to inflict bodily harm on him before, as he returns the borrowed cable to Eve, she hears him stage whisper words that from anyone else should sound defeated. He's delivers them like it's a brag.

"Guess I'm sleeping on the couch tonight, then."

* * *

><p>When they walk into the loft there is a lot of hugging. Castle and Alexis, Castle and Martha, Alexis and Martha … Beckett tries to stay out of the fray and fails miserably. In the confusion, she ends up in Castle's arms, trapped against his broad chest, and <em>wow<em>, he gives the best hugs ever. How has she never hugged him before? Well, maybe there have been some innocent side hugs, but not a full on, no holds barred, all encompassing full-frontal hug.

She'll just give herself one second to hold onto him. Just one second. To let the pressure of his arms wrapping around her ribcage melt the hours of worry away. She locks her arms around Castle's neck and lets her cheek rest on his shoulder. Just for a second.

The room goes awkwardly quiet. Oh no. Beckett is fully aware of the palpable energy they seem to create whenever they touch. Usually it's a brush of fingers on a coffee cup here, a bump of elbows on the sidewalk there, never a full hug. The room is humming with it.

This is why she does not let him hug her.

The thought alone makes her feel like a failure. He deserves better. He deserves a Kate that doesn't bristle when he touches her. She wants to be that so badly. She's trying to be ready, she really is, but suddenly she's swamped by how thoroughly she's sucking at it.

She takes a deep breath. She doesn't have to let go right away, right? She can give him that. And. Maybe. Maybe she can make a gesture, just a small one, a brush of her nose against his neck -

"So, kiddo, you gonna tell us where you were?" Martha's sing-song voice slices through the mounting tension.

"Mother," Castle groans. She's becoming disturbingly talented at interrupting his romantic moments.

Beckett retracts her arms, resigning herself that now is not the time for small gestures. Not when his mother and daughter are right there, watching her every move. Reluctantly, she steps out of Castle's embrace. Tries not to shiver when his fingertips stay at her waist for a fraction of a second longer than necessary.

"I was at a diner, writing. You know ladies, not that I don't appreciate everyone's concern, but I'm a big boy now. I'm allowed to write in a diner all day if I want to write in a diner all day."

Summoning up her earlier frustration, Beckett levels a glare on him.

"Next time you disappear, Castle, I'm sending the SWAT team in to collect you. Just to embarrass you."

"Fine, fine." He holds his hands up in mock surrender. "I'll be sure to keep my phone charged in the future. Ugh."

"Well, now that I've returned you to your nest, Castle, I'd better get going. Got to be up in a few hours for work."

Martha and Alexis descend on Beckett with more hugs, and at last she's on her way to the elevator, expecting to hear the door of the loft click shut behind her.

But then Castle's there, touching her elbow, and they're alone in the carpeted quiet of the hallway, and he's looking at her with such sincerity in his eyes that her stomach drops.

"I'm sorry, Kate." His voice is low. Irresistible. No one does apologies quite like Rick Castle. "I'm sorry I worried you."

She clears her throat. "It's okay. You're okay. Just don't do it again, alright?"

"I won't. Goodnight, Kate."

She loves her first name on his lips. It hints at who she used to be, who he believes she can be again. He's close enough that she can smell the maple syrup on his breath and the woodsy, spicy scent of his body wash.

_Focus, Kate._

"We'll be starting at the precinct at eight tomorrow morning. If you want to come in," she says.

"I'll be there." Castle gives her a warm smile and turns to go.

In the hush of the hallway, the day collapses in on her. The fear that she'd lost him has left a visceral ache in her chest. She wishes they were at a place in their relationship where she'd be able to say how thankful she is that he's still here. She wishes she could just hug him for hours, breathe him in, touch him, and suddenly the daydream of it all is clamoring to get out, forming a word on her tongue, forcing a word out of her mouth -

"Hey."

He stops. Looks back.

"I'm really glad you're okay, Castle."

They nod at each other, two tiny smiles damming up two identical floods of emotion. There's so much there: need, respect, desire, and a deep fondness borne of years of partnership and friendship. The waters of it are high, surging, and the dams are not going to last much longer.

Castle wishes he could tell her how much he loves it when she bites her thumb like that, how she manages to be simultaneously adorable and sexy when she ducks her head shyly, hair falling over her face. Soon, he promises himself.

Kate stays calm as she presses the button to call the elevator. It's only when the doors slide shut that she lets herself slide into the corner, forehead dropping against one wall. All she wants tonight is to stay with him, even if it's just to stand in his foyer trading words. Soon, she promises herself.

Castle locks the front door to the loft and finds himself alone, grinning like a loon.

Later, in bed, before he turns off the light, he checks his phone.

He considers texting her, but that reminds him of his mother's text.

_'Richard. I think that's quite enough. Katherine is crying in your kitchen.'_

He'd felt guilty enough as it was about today, but that text will haunt him. Tears? From Kate Beckett, tough gal extraordinaire? The thought both cripples him and buoys him. Because it means she cares. More than he'd ever dared hope.

Kate's passed this test too.

Flying colors.

* * *

><p><em>Thoughts?<em>


	4. Committing

_A/N: Castle has tested Kate's desire for him and her concern for his well being. Time for the third and final test._

* * *

><p><strong>Chapter Four<strong>  
>Committing<p>

* * *

><p>He loves going to weddings with her.<p>

At weddings, she slides towards the softer end of the Kate to Beckett spectrum. At weddings, her hidden romantic side - the one she does such a good job of hiding - starts to cautiously bloom. At Kyra's wedding she'd looked so soft in her rose petal blouse, all of her broken glass edges ground down just for a night.

In the little Catholic church where Kevin and Jenny had recited their vows, she'd been unlaced than he'd ever seen. He hadn't been able to keep his eyes off her. Leaning forward in the pew, eyes bright and wide, she looked for all the world like a little girl who believed in fairy tales, and all he could think of in that moment was how he wanted to be the one to make her dreams come true. Later, they'd danced, only once, but he was hooked.

Tonight, she's beside him at different wedding, but she's wearing the same starry-eyed look as she smiles at the bride and groom dancing a few feet away from them. In Castle's not-so-humble opinion, Kate is glowing far brighter than the sweet second grade teacher his friend Paul is marrying.

He'd met Paul on the one and only writing retreat he'd ever attended, six weeks before Black Pawn picked up _In A Hail of Bullets_. He was about to decline the wedding invitation, but it was too tempting of an opportunity to rope Beckett into a date. "Come, on, Beckett," he'd whined. "You're my only friend that's not a guy." He'd tossed in a pout and told her Alexis had turned him down. Honestly, he hadn't even asked, just in case Alexis had said yes. She'd given in without too much trouble, and the past four hours have been a blur of vows and applause and good food. He's hoping he can keep her a little while longer, even though he'd said they could leave whenever she wanted to.

A new song starts, slow and jazzy, with an irresistible beat. He can almost feel the swing of the music pulling the final threads of tension out of Beckett's taut frame. He's enjoying the warmth of her upper arm pressed against his, gauging if she's relaxed enough to ask out on the dance floor.

But she beats him to it. She leans into him, nudging him almost to the point of tipping. "Let's dance, Castle."

"Thought you'd never ask." He lifts a brow. "No, really, I didn't think you'd ever ask."

He turns and offers his hand, but instead of taking it, she loops both arms around his neck. His hands land on her hips, maybe lower than strictly necessary. The deep green velvet of her dress feels magnificent. He holds his breath and slides his palms down so that his fingers meet over her lowest vertebrae, but miraculously, she stays quiet, and then she's swaying, swinging, moving perfectly in time to the pulsing bass line of the music.

"Mmm," she purrs. "I love Alicia Keys."

Whoa. Beckett does not say stuff like this. She's had two Jack and Cokes, and there was the endless round of champagne toasts, but she's not a lightweight. She's steady in his arms despite her higher than usual heels.

The way her body is moving is doing all sorts of things to his concentration levels - and his imagination. And right now, Castle is imagining her dancing alone in her apartment. In the scene unfolding in his mind, she's wearing black boy-cut underwear and a white spaghetti strap that clings to her so tightly she might as well not be wearing anything. Definitely no bra. She's at the stove, stirring something in a bright saucepan (apparently in his imagination she doesn't always eat takeout). She's barefoot and swaying to the only Alicia Keys song he's familiar with, her hips knocking left and right to the lyrics _'I keep on fallin' in and out of love with you.'_

With sudden clarity, he knows that she _has_ danced to that song, and thought of him whilst doing it. The song suits them, paralleling the ebb and flow of the last four years, of her pushing him away one moment and letting him a bit further in the next. It's always been two steps forward and one step back, though. Tonight is a testament to how much she's warmed up to him since they met, and how much his respect for her has grown.

The song playing now is different to the one in his daydream, not one he's heard. The amplifiers are pointed away from them and the subwoofer drowns out the lyrics, but Castle manages to make out some of the words. Something about a woman's worth, and '_a real woman knows a real man always comes first.'_

He chuckles when she quirks an eyebrow at him and mouths along with the lyrics '_I'll hold you down when shit gets rough' _like it's her favorite line of the whole song, a laugh on her lips. God, this is why he loves her. She's so fun, just as silly as him, only she doesn't let just anyone see it.

The way she's moving makes him bold. He loves that he doesn't even have to bend down to whisper in her ear. He lets his lips touch her skin, just briefly. "Mmm, yeah, it's a pretty good song actually. Can't say I agree with all the lyrics, though."

"I dunno, Castle, I think I do a pretty good job of holding you down when shit gets rough."

It's true, they have held each other down. Been each other's solid ground through more ridiculously rough situations than any two people should get into. She's still smiling, so he knows she's not thinking about the one time he had to _literally_ hold her down, behind the hanger as Montgomery faced down her hunters. But that's not what he really wants to talk about.

"Not the line I was referring to."

For a moment she looks puzzled, rewinding the lyrics in her head, and then suddenly she gets it. He can tell because she swallows so hard he can hear it.

"I'm a firm believer that the woman should _come _first," he says.

He's a firm believer, alright. He'd better step back before she notices. He's pretty sure from the first test that she wants him, but tonight's not about finding that. Tonight is about finding out if she wants a serious, long-term relationship with him. If she'll let him have a shot at being her one and done.

He cringes inwardly, regretting his words. If he's read her wrong - if she's not interested in him at all, the evening is about to crash down around them. Because this isn't their normal brand of sexual tension - this time it's serious, not light and playful. If she doesn't feel the same electricity crackling between them, she'll come down hard on him with eyes iced over. He'll be on is own in seconds. If she's as affected as he is by the proximity they've shared this evening, by the heat captured between the curves of their stomachs, she'll run anyway, but not far.

"You know what? I could use another drink," she says.

And just like that, she's gone.

He watches as she crosses the room, taps her fingers on the polished wood of the bar while she waits for her drink.

While she's occupied, he takes the opportunity to skirt the crowd of dancers to the table set up on the far end of the room. Then he slips the DJ fifty bucks and a portable USB stick with a single mp3 on it.

* * *

><p>She's perched sideways on her chair, watching the jumping neons on the floor with a zoned out, almost dreamy look on her face when Castle he hears the opening notes of the next song. His song. He pulls her up and into his arms, angling them onto the dance floor. She opens her mouth to protest, but there's no time. He needs her to listen.<p>

"Shh." He breathes it into her ear. She can be stubborn as hell, but she gentles against him now. She wouldn't give in if it were the first dance of the evening, but she's slowly become acclimated to being held by him over the course of the evening.

Castle gives her a minute to listen, to absorb the words and the helpless devotion in the melody.

_You are all that I taste _

_at night _

_inside of my mouth_

He wonders if she remembers how their kiss tasted.

God, he'll never forget it. At first her lips were cold; they tasted of ice and crisp night air. But then she'd opened to him, and he lapped up the flavor of her, something warm and rich and indescribably Kate, laced with a hint of vanilla latte.

The first kiss was calm. She tasted practical and steady, reminding him of how she does such an amazing job of tempering his zaniness.

But the second kiss - the second kiss tasted like desire. Heat. Abandon. And he knew that she was in it as far as he was if he could make her lose control like that with just a kiss.

But the whole time she'd tasted like home.

_You are in my veins _

_and I cannot get you out_

Halfway through the song, he prepares to ask The Question, dropping his voice so she knows how important this is.

"What about this one?"

"The song? What about it?" she asks.

"Do you agree with these lyrics?" Here it comes. The moment of truth. "Kate - do you think you'll ever get me out of your veins?"

He prays she won't go for levity. It's his job to bring that to the relationship, but he doesn't want it right now, doesn't want her to pick up the mantle if he drops it this time. He doesn't want her to make some snarky allusion to how she'll never shake him off, like he's just a clingy puppy nipping at her heels. He doesn't want her to act like she doesn't want him there beside her every day.

She startles at the question and looks up at him. He sees something entirely new in her eyes that might be fear, but not the same kind of fear that makes that makes her go out and do brazenly stupid things in the name of justice.

"Who said you were in them?" she asks. Her voice is low and raw.

"They did." He brings her wrist up so they can both see it, and he circles his thumb over the blue vein of her pulse. Sure enough, he can feel the quickening of her heartbeat, watches as her blood brings a blush to her cheeks.

"So. Do you?" he asks.

She stares intently at the undone button at the collar of his shirt.

"Kate. Do you think you'll ever get me out of your veins?"

At the almost imperceptible shake of her head, his heart attempts a jailbreak from the cage of his ribs.

She follows the uncharacteristically shy little gesture with a steady, simple verbal answer.

"No."

And then she hides her face in his shoulder, mumbling into his shirt, breathing heat into his skin.

"No, Castle, I probably never will. Now shut up and just dance with me. You're not getting any more out of me tonight."

He complies.

* * *

><p><em>AN: Hopefully this chapter did a little to rectify Castle's bad behavior in the last two chapters. Thank you for not giving up on me! Next chapter probably won't be until after Christmas, so have a very happy holiday wherever you may be. If you're hungry for fics, there are a lot of wonderful stories from the Summer Ficathon, including my completed piece, if you haven't gotten around to them yet. Have fun!_

_-Bri x_


	5. Confronting

.

* * *

><p>Chapter Five<br>Confronting

* * *

><p>A week after they attend his friend's wedding together, Castle sends Kate a text.<p>

_Hey - I need your advice on something. Can you come by?_

The day and time might seem arbitrary, but for Castle it meets a very specific set of conditions. She'll be comfortable - she'll have changed out of her heels and slacks and into yoga pants and fluffy socks. They closed an easy case yesterday, so she'll have had a decent sleep the night before. To top it off, she doesn't have to work tomorrow. She'll be sliding into Kate, and that's just how he wants her.

He plucks an apple from the fruit bowl and rolls it from hand to hand as he eyeballs his phone. He wonders if she's on the couch with her feet tucked up warm under her thighs. She's probably looking forward to not venturing back out into the world for at least twelve hours. He imagines her blowing out a sigh when her phone chimes. He crosses his fingers that she'll agree to come over, because he's a pretzel of emotions and he desperately needs to talk to her.

The whole week has been a roller coaster ride of confusion. Even though his experiments produced spectacular results, ones that should buoy his confidence, he still doesn't know where he stands with her. And while he would probably wait another four years for her, he just needs to hear something solid from her lips. Not some cryptic promise about a hazy future. Unfortunately, going about things in his own sneaky way (his mother's words, not his) had served only to whip him into an even bigger frenzy.

He supposes he deserves to spend some time in turmoil. He's still haunted by her tears. He was stupid for thinking his diner stunt wouldn't hurt her.

He's not sure why he feels so much more insecure about her feelings for him. So far his hypothesis has held. The facts are definitely there. All the evidence he's gathered points to Kate Beckett being in love with him. But they've solved cases where the evidence says one thing and the truth says another. The only thing that will make him believe is hearing it from her lips.

He is so ready for this confrontation. He's not about to wait for her to find another Josh and waste yet another year.

He swipes at his phone, checking his text log just in case the notification didn't come up on the lock screen.

They've been getting closer, more like true friends every day. The number of out-of-hours texts have been multiplying. Each one he gets in return is an exhilarating little morsel that makes his pulse rush like a damn teenager's. Somehow - and he didn't really think this would happen - they've never metered their reply times, have never played games or pretended to be busy when they weren't. He's never had to wait more than half an hour to hear back from her. It's a very refreshing change from the other women he's dated or been married to.

He puts the phone down and tries to breathe.

A month ago, she might have been alarmed by his simple request. She would have overthought it and asked questions and made excuses. Tonight he hopes she'll just say yes, trust that he wouldn't ask if it wasn't important.

Suddenly the screen illuminates, and his thumb flicks over his password before the alert sound even ends.

_Give me a few minutes to change. Are you going to feed me?_

He grins as he taps out a response.

_Sure thing, but don't change on account of me. What are you in the mood for? Sushi, yakitori, gyoza?_

_All of the above. And before you ask, no I'm not scantily clad._

_Wouldn't dream of asking. Might just dream though._

_Mmmhmm._

He grins down at the word she's texted him most often. He knows the exact intonation of her _mmmhmm_, how it sounds more like a sardonic _yeah I'll just bet you do, _but he loves imagining the word with an entirely different inflection. A sexy inflection.

_Ordering now, _he texts._ See you soon._

* * *

><p>He keeps the TV on so she won't notice right away how devoid of redheads the loft is. They watch a ridiculously bloody Robert Rodriguez film while they feast on an equally ridiculous spread of Japanese food. Even the cuisine was a strategic decision - it doesn't dull his senses like Chinese, get him antsy and fired up like spicy Thai, or send him into a coma like Italian.<p>

He has a strategy for everything tonight. Everything has to be perfect. He wants this to be the beginning of them.

They maintain a respectable distance on the couch, leaning forward every now and then to collect more food. She's sitting cross-legged, turned towards him slightly, and the two feet of space between them doesn't do much to tamp down the occasional flare of heat when it sinks in that they're together and alone, without even daylight to chaperone. But most of the time it's relaxed and _them_ and just perfect.

Every now and then her bare toes wiggle, seemingly independent of her body, and it takes an inordinate amount of effort not to reach for her feet, run his thumbs over the high gloss of her red nail polish, pull her arches into his hands and make her purr with his considerable massage skills.

When she caves he's going to spend absolutely hours exploring her.

He has no idea that she's caught him looking at her. More than once. She hides her smile behind her hand.

Finally, she leans back and rests her hands over her stomach. "I should probably quit while I'm ahead."

He pauses the movie and they bend forward to pack away the leftovers.

"Thanks for dinner, Castle." They've done this enough times that they know they can skip over the platitudes, the '_oh let me help' _and the '_don't be silly you're the guest.' _They work efficiently alongside each other in this as in everything else, hands brushing a few times as they tidy up, but never reaching for the same box. They're comfortably in orbit.

When the last of the cardboard boxes is tucked into his fridge, Castle makes his first move.

As she's walking back towards the couch, he redirects her towards his office by laying his palm on the small of her back, just low enough to feel where her tailbone starts to curve out. Her steps stutter, and even though it was a calculated move on his part, she recovers faster than he does. He didn't realize how warm she'd feel, how close he could get to her skin through the thin material of her top. The touch runs through his body like a shock, and when he speaks, his voice comes out a little rougher than intended.

"It's in my office. The um, thing I need your opinion on."

She doesn't speak, just nods and forces her feet to move, to step forward even if it means breaking contact with his hand.

He lets her open the office door and follows her inside. He watches as she scans the room. She's never been shy about looking at everything in his loft, and he's not sure if it's a cop habit or if it's because she's trying to gather as much information about him as he's gathered on her.

So of course she spots the handcuffs, laying conspicuously in the center of his desk. She sidles up and traces one metal circle with her fingertip, her mouth curving up into a smile for just a fleeting moment before she schools her features.

"Order these from Amazon, Castle? Thought you might have gone for fur-lined."

He steps up behind her, a little too close, edging in slowly so he doesn't spook her. Here goes nothing.

"I've never actually cuffed anyone," he starts, adding a practiced layer of uncertainty to the statement.

She turns to face him with an almost jaunty grace. He's impressed that she's keeping her cool. She gets it, of course.

"Seriously? You want to try cuffing me for _research_?"

"Well you did say next time … and there aren't any tigers in here. I even made sure Alexis's stuffed animal collection didn't include a wildcat of any description. It's just - I'm writing this intense chase scene and Nikki cuffs the guy at the end, and I know I've seen you do it dozens of times, but I've never actually done it and I don't think I'm getting it right."

He swallows hard through a very pregnant pause. She just stares at him, and he can't tell if she thinks he's abominably stupid or kind of adorable. That's not really a new look, to be honest.

"Fine," she says. It's a strong, lilting challenge, and it makes him fall just a little bit harder for her. He lets out a breath he wasn't aware he'd been holding.

"Okay. So I can't decide if Nikki's going to slam him up against a wall or dive into the backseat of his car and cuff him to his headrest."

She rolls her eyes. "His headrest? Really?"

"Hey, it could work."

She bites her lip. It could, actually. Although it would probably never happen in the real world.

"Well, I guess we can try both," she concedes.

"Okay."

"Okay."

Neither of them move.

"I don't want to actually slam you into a wall, though," he says. _Well, that's a lie._

_"_Uh, okay, we can pick up from right after the slamming, then." She steps over to the strip of wall between his bedroom door and the bookshelves. "I hope this is the wall you had in mind, because I'm not letting you act out this little fantasy in your bedroom, Castle."

He presses his hand to his heart in mock affront. "I would never! This location will do just fine."

She turns around and presses herself into the wall. "I can't believe I'm doing this," she mumbles. "Okay, so you've run me down, caught up with me and grabbed the tail of my shirt. I'm cornered. You either shove me straight ahead into the wall or you swing me out to the side and slam me against whatever flat surface is available."

He coughs. Hearing her use her Detective Voice to utter that sinful string of words is really doing it for him.

"Put your forearm vertically between my shoulder blades, hand on the opposite shoulder. If I squirm, dig in with your elbow."

She turns her cheek out, rests it on the wall, and waits.

And waits.

She looks like she's about to tell him to get a damn move on when his forearm arrives in the prescribed position. They both go still. His fingers curl over the smooth, round bone of her shoulder and he leans in, pressing his weight into her slowly, gently.

Her eyes close. Just for a moment. If she doesn't stop looking so unbearably hot he'll never be able to go through with the plan. Screw the plan, maybe he should just press the rest of his body into her and see where it takes them. She seems like she might just go with it this time.

"You should have lit some candles and put on some Marvin Gaye. What the hell are you doing, Castle? I'm a suspect. Treat me like one."

Okay, so maybe more persuasion is needed.

She walks him through the rest of the actions. If he didn't know better, he'd think she was a little disappointed that he didn't touch her like that again. They rehearse the scene a few more times, fine tuning it. She gets stuck at one point and makes him reverse roles so she can consult her muscle memory. All he can think is that it shouldn't feel so good to get arrested.

"I think you've got it now, Castle." Her color is high, cheeks flushed. Maybe from being pressed against the wall, maybe from the proximity of his body. He hopes it's the latter.

"Let me try one more time. Gotta make sure it's perfect," he says.

He takes a deep breath. Steels his resolve. This time when he cuffs her, just before she realizes he's not going to immediately unlock her, he's going to whisper in her ear.

_'You're under arrest for the obstruction of the happiness of Katherine Beckett, and for placing unlawful impediments on said victim's well-being.'_

And then he's going to come clean about his experiments, and just ask her point blank if she wants to do this with him, dive in, be there for each other. All the time. Not just at work.

But when she turns to face the wall, there's a gleam in her eye that he can't decipher. And when he starts to slap the metal of the cuffs around her wrists, something sharp - her elbow, probably, plows into his solar plexus. She whirls around and tackles him before he can figure out how to suck in a breath, and the world tilts and goes fuzzy before he realizes he's face down on the floor, his arms wrenched behind his back. The cuffs snap closed around _his_ wrists.

"Jeez, Kate." he wheezes. "I get it, I get it. I left myself open, the suspect could have taken me down." Her knee presses into his thigh, sending a weird ache all down his leg that's going to keep him from walking until the blood's allowed to recirculate. "Could you have made your point a little less painfully?"

"Oh, that wasn't really the point I was trying to make." She's smiling, he can tell. He's missing something.

"Uh - what?"

"You do know I'm a detective, right? Do you think I don't know what you've been up to?"

"Um, I haven't been up to anything - "

Kate twists his ear with her free hand and he squeaks. "Really. You're not as good of an actor as your mom, you know. What's tonight about, huh? You trying to get another reaction out of me?"

"No - what? I - "

"You find out what you wanted to know, Ricky?"

His stomach bottoms out, but he has no choice but to stick to his story, to keep playing dumb. "What? When? I don't know what you're talking about."

"Nice try. You of all people should know that's what they all say. I'm not blind, Castle. There's been too many weird things going with you lately. Don't you think I know by now when you're plotting something?"

He careens, looking for a way to get out of the hole he's dug himself into. He's a fast thinker in situations like this, they both know it. But she's a master interrogator and right now she definitely has the upper hand. After all, his face is half smushed into the carpet. He might even be drooling a little bit.

He groans. He didn't think the first time being pinned under Detective Beckett would be this uncomfortable. Or that he'd feel so unattractive.

"You know what I do to scheming, conniving lowlifes, right?" she asks as she presses down on the cuffs. The metal digs into his wrists painfully, recalling bruises that have only just faded from their day spent in the basement.

"I - I didn't - I wasn't thinking - I don't - um -" he whines. "Please don't punish me."

Suddenly, the pressure lets up. Kate lets out a muffled snort. He can feel the ends of her hair brush against his neck, so she must be folded in on herself …laughing? The pressure eases on his thigh and he can feel the crawling tingle of blood rushing down.

"God it's fun to make you squirm," she says, gulping with laughter.

He's completely thrown. He was definitely not expecting this reaction. To be honest, he expected her to be a little pissed off. He'd hoped that the peaceful camaraderie of the evening he'd created would take the edge off of her anger.

"So … you're not mad?"

"Mad? No. I didn't figure out you were up to something until the day after the wedding, and while we were dancing you'd been so … I dunno, kinda sweet, I guess. Just one question, though. What exactly was the goal of all of it? What were you trying to get out of me? You don't have to dig for compliments, Castle, I'm sure there are lots of women out there who'd give them to you for free."

"I'd rather have this conversation in a more dignified position if you don't mind," he says.

"I'll help you sit up. But I'm not going to release you let, Castle. Not sure I can trust you not to try to cuff me. That is what you were going to do, right?"

He sputters, then sees the futility in arguing with her.

"How'd you know I was going to?"

She raises an eyebrow. "It seems you've completely forgotten that I'm a cop."

He leans gingerly against the wall and she slides down to sit on the floor beside him. Not close enough to touch, he notes.

"So you're not mad? Not even about the day my phone was off?"

She turns to him, eyes blazing.

"You did that on purpose?"

Uh-oh. He slumps against the wall as she seethes.

"What the hell, Castle?"

"I take it that means you're not going to un-cuff me anytime soon."

"No." She crosses her arms, shutting down on him. "Jesus, Castle, you scared us sick. Your - oh." He watches it dawn on her, watches as her eyes flatten and dull. "Your family knew." He can see the hurt race across her face, the embarrassment that he played her, reduced her to a sloppy mess in front of Martha and Alexis just to see if she'd react the way he desperately wanted her to.

"I'm sorry, Kate. It was so stupid of me. You know me, I didn't really think it through, and then when I saw how concerned you were … but I've been a wreck about it all week. I just wanted to see if you cared, but I know now that wasn't the way to handle it."

"If I cared? You're my partner, of course I care if you go missing."

"I didn't doubt that you'd look out for me as your partner. But the way you reacted - it was more than it would have been for Esposito or Ryan, right?" he asks. He's got to walk on eggshells if he wants this conversation to get back to where he wants it to go.

"I would have worked just as hard to find them."

He scoots closer to her, nudging her with his shoulder to get her to look at him. "When we hugged in the hallway… would you have held on for as long if it had been one of them?"

She blushes and looks away.

He almost groans, wishing for just one straight answer out of her instead of so many deflections.

"When did you catch on?" he asks, trying a different route.

"You weren't very subtle with that song at the wedding," she says. "It was pretty obvious that you got the DJ to play that for us. That's what tipped me off. After you dropped me off at home, I got to thinking, and I realized that ridiculous game we played at Sports Day was a set up too. Again, I don't get what you were trying to get out of me. I hope to God you weren't just trying to embarrass me in front of the entire precinct."

"No, Kate, God, no. I'd never do that." If he could hide his face in his hands he would. "It was stupid. I was just feeling insecure. I thought I could get a little boost of confidence, something to keep me going. I've just been so confused. But I shouldn't have done it, because it upset you, and it didn't help anyway."

She's quiet, and he turns his head to look at her. She's staring at her hands, her mouth pressed into a line thin with something that looks like regret.

"What do you mean it didn't help?" she asks.

"Because I'm still confused. Even though the results of my, uh, experiments were favorable, it's still not black and white enough for me. I'm just a guy, Kate. A stupid, blundering fool, and I need you to spell it out for me. I thought - I thought you meant me, on the swings. But then so much time passed, and things were like they used to be, only I still went to sleep every night thinking about you, and - "

"I did mean you."

He takes a hard mental stumble.

"You did?"

"Yeah. Thought that was pretty obvious."

"Not obvious enough for me. Obviously."

The corner of her mouth quirks up.

"So … these little tests you were putting me through- "

"Experiments."

"Experiments, then. Tell me about your findings."

"Well, the first test, the toilet paper game, that was to find out if you wanted my hot sexy body, obviously."

"And?" She lets her gaze drop, gives him a once over that almost has _his _toes curling.

"Um."

"Castle? Focus."

"How am I supposed to focus when you look at me like that?"

"So? Do I want your hot sexy body or not?" she asks, tugging her lip between her teeth.

He shakes his head. "You're such a tease. I'd do something to level the playing field if my hands weren't tied behind my back."

She laughs. This feels right. This feels fun.

"According to my findings," he says, "yes, you do want me. But I can assure you, it's not nearly as much as I want you."

"Well, we'll just have to see about that," she purrs, nearly knocking him off his game.

"Detective, you're so feisty when you let your guard down."

She shrugs. "What's the point of not going all in? I've been waiting a long time for this, Castle. It was always going to be all or nothing, when I finally made a decision. Sorry it took so long," she adds after a long, quiet breath. "So what else? The day you turned your phone off. What did you learn then?"

"The second test, like I said before, was to find out if you cared about me. About my well being, as more than a colleague. Outside of the precinct, when I could be 100% sure that keeping me safe was more about avoiding paperwork."

"You know it's been about more than avoiding paperwork for a long time. If something happened to you I'm not sure I'd recover." Something dark passes over her features.

"I know. I feel exactly the same. We don't have to dwell on it, because it'll just make our jobs harder. Let's just keep having fun and solving crimes, okay?"

"Okay, yeah."

"The third and final experiment - the wedding - well, I wanted to find out if you thought a relationship between us could last."

"And?" she asks. He wishes he could smudge the murky hesitation out of her eyes. This is the one she's having the most trouble with.

"You passed all three tests beautifully, Kate. And if you're crazy enough to want to be with me, I'm sticking. For as long as you'll have me. I can't promise you I'll be perfect, if that's what you're worried about. I'll probably screw up. A lot. But I have never, and will never, love anyone as much as I love you."

"I don't know if I'm ready," she whispers.

"Maybe it's like what they say about having kids - that you'll never really be ready. You just have to learn as you go."

"Alright." She takes in a ragged breath, runs her hands over her thighs. "So you want some concrete evidence, huh?"

He doesn't trust himself with words, only nods.

"Okay then." Kate studies his face, brings her hand up. She strokes one thumb down his cheek and he almost shivers with the pleasure the small, perfect touch brings. "Let's do this. I want to be with you, Richard Castle. You're the only one I want to be with, the only one who's seen all of me and stands by me anyway. I want to try…" she takes a deep breath, "being in a relationship. With you, Castle."

He blinks through the sudden surge of emotion her words bring with them.

"Those are the best words I've ever heard."

Then she bites her lip and smiles. She's so damn beautiful. He clears his throat to thin the rising choke of his love for the stunning, luminous woman beside him.

"I'd like to do another experiment," he says. "You know, just to test the hypothesis one more time. Even though your confession would hold up in any court."

"Oh?" Her eyes search his, a pool of amusement and hope swirling before him. "What kind of experiment?"

Castle leans in, lets his gaze fall to her lips. "I think I should kiss you."

She grins. "Cuffs on or off?"

He'd almost forgotten he was still wearing them.

"On to begin with, if you'd rather. You're in control here, Kate. But all of my highly scientific experiments suggest that you won't find the experience completely miserable. And if you like it … well, then we can try it without the cuffs too."

He's so close now. He nudges her nose with his, her lips sweet and warm and falling open.

"Well, I guess it couldn't hurt, just to experiment," she whispers.

She's smiling when he takes her mouth.

It's soft. Sweet. And when she pulls back, there's wonder in her eyes. And then their lips meet for a second time, and just like their undercover kiss, it heats up _fast_. Her mouth is velvet under his, their lips crushing together in perfect rhythm.

He slides into her mouth and works to drag out the sexy little groan he remembers so vividly from the alley. Only this time, her lighting fast move isn't a roundhouse kick - it's her leg shooting over his lap, clamping her knees on either side of him. She settles herself onto his thighs and grabs his face, and proceeds to kiss the ever-living breath out of him.

He's about to ask if he can take the cuffs off when he feels her wedge her hands between his back and the wall. He hears the snick of a lock opening and the cuffs fall to the floor, forgotten, as his arms wrap fast and tight around her, pulling her body up against his from navel to neck. She tosses her head back on a gasp, tearing her lips from his, as if the sensations are too much to bear. He dives after her, latching onto her bottom lip and pulling her down with him.

* * *

><p>They don't make it to the bed.<p>

The first time.

The mattress is cooling underneath them when Castle wonders aloud if he should change careers.

"Oh?"

"I could totally be a scientist. Not only was my hypothesis 100% correct, I think I just tested it very thoroughly."

"Mmm, very thoroughly," she agrees. "But I think I'd rather you stick with your day job, Castle."

"Yeah. I do have a smokin' hot partner."

She swallows his irreverence with the hard press of her mouth and the swing of her hips.

* * *

><p>AN: I've been the queen of procrastination and have had such a hard time with this story, but you deserved an ending so I worked very hard to give you one. Sorry for its utter rubbish-ness. Thank you all so much for reading and for your encouraging words along the way. Happy New Year and have a very happy Castle Monday tomorrow!


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